Alan Pradel, American Museum of Natural History, Department of Vertebrate Paleontology, New York

Toni L. Ferrara, Computational Biomechanics Research Group, Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales,Sydney, Australia

ISAF 2010 Worldwide Shark Attack Summary (REVISED: 1 February 2011)

The International Shark Attack File (ISAF) investigated 115 alleged incidents of shark-human interaction occurring worldwide in 2010. Upon review, 79 of these incidents represented confirmed cases of unprovoked shark attack on humans. "Unprovoked attacks" are defined as incidents where an attack on a live human by a shark occurs in its natural habitat without human provocation of the shark. Incidents involving sharks and divers in public aquaria or research holding-pens, shark-inflicted scavenge damage to already dead humans (most often drowning victims), attacks on boats, and provoked incidents occurring in or out of the water are not considered unprovoked attacks. "Provoked attacks" usually occur when a human initiates physical contact with a shark, e.g. a diver bit after grabbing a shark, a fisher bit while removing a shark from a net, and attacks on spearfishersand those feeding sharks. The 36 incidents not accorded unprovoked status in 2010 included 22 provoked attacks, 3 cases of sharks biting marine vessels, 4 incidents dismissed as non-shark attacks, 5 "scavenge" incidents involving post-mortem bites, and 2 cases in which insufficient information was available to determine if an unprovoked shark attack had occurred. In time, as further evidence is gathered, some of the latter may be assigned to one of the alternate categories.

The 2010 yearly total of 79 unprovoked attacks was higher than the 63 unprovoked attacks 2009 and the highest since 2000 (80). The number of unprovoked shark attacks has grown at a steady pace over the past century with each decade having more attacks than the previous. The growth in shark attack numbers does not necessarily mean that there is an increase in the rate of shark attack, rather it most likely is reflective of the ever-increasing amount of time spent in the sea by humans, which increases the odds of interaction between the two affected parties.

The number of shark-human interactions occurring in a given year is directly correlated to the amount of time humans spent in the sea. As world population continues its upsurge and interest in aquatic recreation concurrently rises, we realistically should expect increases in the number of shark attacks and other aquatic recreation-related injuries. If shark populations remain the same or increase in size, one might predict that there should be more attacks each year than in the previous year because more people are in the water. Shark populations, by contrast, actually are declining at a serious rate or are holding at greatly reduced levels in many areas of the world as a result of over-fishing and habitat loss, theoretically reducing the opportunity for these shark-human interactions. However, year-to-year variability in local economic, social, meteorological and oceanographic conditions also significantly influences the local abundance of sharks and humans in the water and, therefore, the odds of encountering one another. As a result, short-term trends in the number of shark attacks - up or down - must be viewed with caution. Thus, the ISAF prefers to view trends over longer periods of time (e.g., by decade) rather than trying to assign too much significance to often high year-to-year variability.

In addition to increases in the number of hours spent in the water by humans, the ISAF's efficiency in discovering and investigating attacks has increased greatly over the past decade, leading to further increases in attack number. Transfer of the ISAF to the Florida Museum of Natural History in 1988 resulted in greatly expanded international coverage of attack incidents and a consequent jump in the number of documented attacks. In the early 1990's the ISAF was able to develop important cooperative relationships with many Florida beach safety organizations and medical facilities, leading to increased documentation of attacks from a region that is a world leader in aquatic recreation. Fundamental advances in electronic communication (the Internet and email), a greatly expanded network of global ISAF scientific observers, and a rise in interest in sharks throughout the world, spawned in part by increased media attention given to sharks, have promoted more complete documentation of attack incidents in recent years. The ISAF web pages which include electronic copies of the Attack Questionnaire in four languages as well as a plethora of statistics and educational material about sharks, comprises the most highly accessed shark site on the Internet. Our strong web presence regularly results in the receipt of unsolicited documentation of shark attacks. Many of these attacks likely would have been missed in the past because they occurred in communication-poor locales or areas lacking ISAF representatives.

Six fatalities resulting from an unprovoked attack occurred in 2010, only slightly above totals from recent years (the 2001-2010 yearly average was 4.3). These unprovoked fatalities were recorded from Egypt (1), Australia (1), South Africa (2), Florida (1), and California (1). The number of serious attacks in 2001-2010, as measured by fatality rate (7.0%), has been lower than that of the decade of the 1990's (13.0%), continuing a twentieth century reduction trend reflective of advances in beach safety practices and medical treatment, and increased public awareness of avoiding potentially dangerous situations.

As in recent years, North American waters had the most(42%: 32 attacks) unprovoked attacks in 2010. The total of 36 attacks in the United States (including four in Hawaii) wason par with the 2001-2010 decadal average of 38.6. Elsewhere, attacks occurred in Australia (14), South Africa (8), Vietnam (6) and Egypt (6), with a single incidents reported from the Bahamas, Brazil, Fiji, Madagascar, Mascarene Islands, Solomon Islands, Canary Islands, Tonga, United Arab Emirates. Surfers (50.8% of cases) and swimmers/waders (37.7%) and were the recreational groups most often involved in shark attacks in 2010. Less affected were snorkelers/divers (8.2%) and those using inflatable rafts and inner-tubes (3.3%).

Following recent trends, Florida again had most of the unprovoked attacks in the United States. The total of 13 attacks was the lowest total since a dozen incidents were documented in 2004 and fell well below the 2001-2010 average of 23.1. Additional U.S. attacks were recorded in North Carolina (5), California (4), South Carolina (4), and Hawaii (4), with single attacks occurring in Georgia, Maine, Washington, Oregon, Texas, and Virginia. Within Florida, Volusia County had the most incidents (6). This area normally has higher numbers of shark-human interactions as a result of very high aquatic recreational utilization of its attractive waters by both Florida residents and tourists, especially surfers. Other Florida areas having attacks in 2010 were St.Johns (3), Duval (2), Brevard (1), and Martin (1).

Despite continued human population growth and increased interest in aquatic recreation, the number of shark attacks has generally leveled off, averaging 63.5 per year worldwide since reaching a high of 80 in 2000. Likely reasons include:

1. Less people in the water in traditional high shark-human contact areas. Post-9/11 slow-downs in local economies and the recent economic downturn have reduced the number of tourists entering the sea. Meteorological conditions also have played a role - the large number of tropical storms that battered Florida and other U.S. east coast states in 2004, 2005 and 2006 significantly reduced the amount of time spent in the water by humans in these areas. Since Florida annually has more attacks than any other region in the world, the large drops in number of attacks in this region during 2004-2006 is reflected in the worldwide totals in these years.

2. Less sharks in the water. Worldwide over-fishing of elasmobranchs (sharks and their relatives, the skates and rays) has left many populations at critically low levels. Nearshore sharks are the most affected because they are easily captured and are highly sought for their flesh and especially for their fins, which fetch a high sale price and are exported to eastern Asia, where they are used in shark fin soup, an expensive delicacy. The nearshore area is where humans most often enter the sea.

3. Humans may be getting smarter reducing their interactions with sharks. Media coverage of sharks has been high over the past decade with a plethora of television and print stories detailing the "do's and don't's" involved in reducing shark-human interactions. It is possible that those engaged in marine aquatic recreation (and beach safety personnel charged with their oversight in many areas of the world) are doing a better job of avoiding high risk areas and times, thereby reducing chance meetings between sharks and humans.

If one is actually under attack by a shark, we advise a proactive response. Hitting a shark on the nose, ideally with an inanimate object, usually results in the shark temporarily curtailing its attack. One should try to get out of the water at this time. If this is not possible, repeat bangs to the snout may offer temporary restraint, but the result likely become increasingly less effective. If a shark actually bites, we suggest clawing at its eyes and gills, two sensitive areas. One should not act passively if under attack - sharks respect size and power. For additional safety tips, see:

The International Shark Attack File, internationally recognized as the definitive source of scientifically accurate information on shark attack, is a compilation of all known shark attacks. In existence since 1958, it is administered by the Florida Museum of Natural History at the University of Florida under the auspices of the American Elasmobranch Society, the world's foremost international organization of scientists studying sharks, skates and rays. Approximately 5,000 individual investigations are currently housed in the ISAF, covering the period from the mid-1500's to present. Many of the data in the ISAF originate from the voluntary submissions of numerous cooperating scientists who serve worldwide as regional observers. Data submitted to the ISAF is screened, coded and computerized. Hard copy documentation, including original interviews and notes, press clippings, photographs, audio/video tapes, and medical/autopsy reports, is permanently archived. Biological researchers and research physicians study investigations housed in the ISAF. Access to ISAF data is granted only after careful screening on a case-by-case basis. Direct access by the press and general public is prohibited since much data, including medical records, is sensitive in nature and is given in confidence. Requests for summary information and non-privileged data are made to the ISAF curator, George H. Burgess.

Are Sharks Color Blind?

ScienceDaily (Jan. 19, 2011) — Sharks are unable to distinguish colors, even though their close relatives rays and chimaeras have some color vision, according to new research by Dr. Nathan Scott Hart and colleagues from the University of Western Australia and the University of Queensland in Australia.

Their study shows that although the eyes of sharks function over a wide range of light levels, they only have a single long-wavelength-sensitive cone* type in the retina and therefore are potentially totally color blind. Hart and team's findings are published online in Springer's journal Naturwissenschaften.

"This new research on how sharks see may help to prevent attacks on humans and assist in the development of fishing gear that may reduce shark bycatch in long-line fisheries. Our study shows that contrast against the background, rather than colour per se, may be more important for object detection by sharks. This may help us to design long-line fishing lures that are less attractive to sharks as well as to design swimming attire and surf craft that have a lower visual contrast to sharks and, therefore, are less 'attractive' to them," said Prof. Hart.

Sharks are efficient predators and their evolutionary success is thought to be due in part to an impressive range of sensory systems, including vision. To date, it is unclear whether sharks have color vision, despite well-developed eyes and a large sensory brain area dedicated to the processing of visual information. In an attempt to demonstrate whether or not sharks have color vision, Hart and colleagues used a different technique -- microspectrophotometry -- to identify cone visual pigments in shark retinas and measure their spectral absorbance.

They looked at the retinas of 17 shark species caught in a variety of waters in both Queensland and Western Australia. Rod cells were the most common type of photoreceptor in all species. In ten of the 17 species, no cone cells were observed. However, cones were found in the retinae of 7 species of shark from three different families and in each case only a single type of long-wavelength-sensitive cone photoreceptor was present. Hart and team's results provide strong evidence that sharks possess only a single cone type, suggesting that sharks may be cone monochromats, and therefore potentially totally color blind.

The authors conclude: "While cone monochromacy on land is rare, it may be a common strategy in the marine environment. Many aquatic mammals ? whales, dolphins and seals ? also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution, in other words, they acquired the same biological trait in unrelated lineages."

*Note: There are two main types of photoreceptor cells in the retina of the eye. Rod cells are very sensitive to light and allow night vision. Cone cells also react to light but are less sensitive to it. Eyes with different spectral types of cone cells can distinguish different colors. Rod cells cannot tell colors apart.

New research suggests that although the eyes of sharks function over a wide range of light levels, they only have a single long-wavelength-sensitive cone type in the retina and therefore are potentially totally color blind. (Credit: iStockphoto/Ian Scott)

Two-headed shark embryo found

A pair of sharks, both with two heads, have been found hidden away in a private collection. This specimen, one of two, had been sitting in a jar since its discovery in 1934, off the coast of Argentina.

Both specimens were male fetuses and were removed from a pregnant female tope shark. As well as two heads, each fetus had duplicated dorsal fins.